As Newcomen had been the first in the previous century to apply the steam engine to practical work--pumping water from mines--so Samuel Brown of England was the first in this century to invent and use a gas engine upon the water. Brown took out patents in 1823 and 1826. He proposed to use gunpowder gas as the motive power. His engine was also described in the _Mechanics’ Magazine_ published in London at that time. In the making of his engine he followed the idea of a steam engine, but used the flame of an ignited gas jet to create a vacuum within the cylinder instead of steam. He fitted up an experimental boat with such an engine, and means upon the boat to generate the gas. The boat was then operated upon the Thames. He also succeeded experimentally in adapting his engine to a road carriage. But Brown’s machines were cumbrous, complicated, and difficult to work, and therefore did not come into public use. About this time (1823), Davy and Faraday reawakened interest in gas engines by their discovery that a number of gases could be reduced to a liquid state, some by great pressure, and others by cold, and that upon the release of the pressure the gases would return to their original volume. In the condensation heat was developed, and in re-expansion it was rendered latent. Then Wright in 1833 obtained a patent in which he expounded and illustrated the principles of expansion and compression of gas and air, performed in separate cylinders, the production of a vacuum by the explosion and the use of a water jacket around the cylinder for cooling it. For William Burdett, in 1838, is claimed the honour of having been the first to invent the means of compressing the gas and air previous to the explosion, substantially the same as adopted in gas engines of the present day. The defects found in gas engines thus far were want of proper preliminary compression, then in complete expansion, and finally loss of heat through the walls. Some years later, Lenoir, a Frenchman, invented a gas engine of a successful type, of which three hundred in 1862 were in use in France. It showed what could be accomplished by an engine in which the fuel was introduced and fired directly in the piston cylinder. Its essential features were a cylinder into which a mixture of gas and air was admitted at atmospheric pressure, which was maintained until the piston made half its stroke, when the gas was exploded by an electric spark. A wheel of great weight was hung upon a shaft which was connected to the piston, and which weight absorbed the force suddenly developed by the explosion, and so moderated the speed. Another object of the use of the heavy wheel was to carry the machine over the one-half of the period in which the driving power was absent. Hugon, another eminent French engineer, invented and constructed a gas engine on the same principle as Lenair’s.